• 한국지반환경공학회 논문집
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• 제18권9호
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• pp.19-31
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• 2017

미국 사례의 경우 항타말뚝과 현장타설말뚝은 동재하시험과 정재하시험 지지력 상관관계 분석에서 좋은 상관관계를 나타내었다. 하지만, 국내에서는 해외에서 많이 사용하지 않는 매입말뚝으로 주로 시공을 하고 있으며, 매입말뚝의 동재하시험 신뢰성에 대해 의문이 많아 동재하시험의 신뢰도를 확인하고자 하였다. 본 연구에서는 LH 현장(천안, 인천, 의정부)에서 PHC 매입말뚝에 대하여 재하시험을 실시하였으며, 동재하시험(EOID 7회, Restrike 7회)과 정재하시험(7회) 지지력을 비교 분석하였다. 그 결과 재항타동재하지지력 및 정재하지지력 평균 값 비교 시 정재하지지력 평균 값이 약 27% 높게 나타났다(신뢰도 : 0.73, 변동계수 : 0.3). 재항타지지력(Davisson 판정 값) 및 정재하지지력(Davisson 판정 값) 평균 값 비교 시 정재하지지력(Davisson 판정 값) 평균 값이 약 27% 높게 나타났다(신뢰도 : 0.73, 변동계수 : 0.2). 동재하시험과 정재하시험의 차이를 줄이고자 본 연구에서는 수정동재하지지력(EOID의 극한선단지지력+Restrike의 극한주면마찰력)을 제시하였으며, 수정동재하지지력과 정재하지지력을 비교했을 때는 그 차이가 9%로 줄어들었다(신뢰도 : 0.91, 변동계수 : 0.2). 또한 변동계수가 0.2로 줄어들어 일관성이 증가한 것으로 나타났다.

• 태양에너지
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• 제12권2호
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• pp.1-8
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• 1992

본 연구는 동계 외기온 데이타의 시각별 변동특성을 파악하기 위하여 연변동 성분 및 기간변동 성분을 제거한 일변동 성분의 매 시각별 외기온 데이타에 대해서 일교차의 발생요인에 대해서 분석하였다. 또한 동계시각별 외기온의 주파수 특성에 대해서 검토하였으며 외기온 데이타의 수식화의 가능성을 제시하였다.

• 한국산업융합학회 논문집
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• 제5권3호
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• pp.247-254
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• 2002

This study has researched the following conclusion to compare to the existing theory and to examine lateral earth pressure, which have measured to add incremental load on sandy soil, and were different in types of compaction by modeling earth pressure test. Lateral earth pressure by incremental load shows that it is increasing at depth forty four centimeters as 2/3H point for wall high, and under 2/3 H point the variation of earth pressure on incremental load is not conspicuous. Therefor, the more a position of surcharge load is close with fixed wall, the more a variation of lateral earth pressure marks considerably. According to relative compaction density of soil, lateral earth pressure turns up larger effective value for layer compaction test to a thickness of thirty three centimeters than layer compaction test to a thickness of twenty centimeters by the roller.

• Structural Engineering and Mechanics
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• 제54권1호
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• pp.87-103
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• 2015

This paper focuses on an analytical research on the critical buckling load of cylindrical shells with stepwise variable wall thickness under axial compression. An arctan function is established to describe the thickness variation along the axial direction of this kind of cylindrical shells accurately. By using the methods of separation of variables, small parameter perturbation and Fourier series expansion, analytical formulas of the critical buckling load of cylindrical shells with arbitrary axisymmetric thickness variation under axial compression are derived. The analysis is based on the thin shell theory. Analytic results show that the critical buckling load of the uniform shell with constant thickness obtained from this paper is identical with the classical solution. Two important cases of thickness variation pattern are also investigated with these analytical formulas and the results coincide well with those obtained from other authors. The cylindrical shells with stepwise variable wall thickness, which are widely used in actual engineering, are studied by this method and the analytical formulas of critical buckling load under axial compression are obtained. Furthermore, an example is presented to illustrate the effects of each strake's length and thickness on the critical buckling load.

• 전기전자학회논문지
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• 제18권1호
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• pp.37-44
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• 2014

In this paper we present an LDO based on an error amplifier. The designed error amplifier has a gain of 89.93dB at low frequencies. This amplifier's Bandwidth is 50.8MHz and its phase margin is $59.2^{\circ}C$. Also we proposed a BGR. This BGR has a low output variation with temperature and its PSRR at 1 KHz is -71.5dB. For a temperature variation from $-40^{\circ}C$ to $125^{\circ}C$ we have just 9.4mV variation in 3.3V LDO output. Also it is stable for a wide range of output load currents [0-200mA] and a $1{\mu}F$ output capacitor and its line regulation and especially load regulation is very small comparing other papers. The PSRR of proposed LDO is -61.16dB at 1 KHz. Also we designed it for several output voltages by using a ladder of resistors, transmission gates and a decoder. Low power consumption is the other superiority of this LDO which is just 1.55mW in full load. The circuit was designed in $0.35{\mu}m$ CMOS process.

• 정보저장시스템학회논문집
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• 제5권1호
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• pp.47-52
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• 2009

Most hard disk drives that apply the ramp load/unload technology unload the heads at the outer edge of the disk while the disk is rotating. The load/unload includes the benefits as like an increased areal density, a reduced power consumption and an improved shock resistance. A lot of papers investigating the effects of the various load/unload parameters such as a suspension tab, a limiter, a ramp and air-bearing surface designs have been published. However, in previous researches, an effect of the suspension is not considered at each load/unload step. In this paper, we focus that a variation of the state matrix affects the load/unload performance on based on a state matrix that is a stiffness matrix of the suspension. Because the state matrix is related to the suspension at each load/unload step, to change the state matrix means the structural change of the suspension. Therefore, we investigated a range of a pitch static attitude(PSA) and a roll static attitude(RSA) for load/unload performance. We also analyzed an effect of the variation of the state matrix a range of load/unload velocity occurred a slider-disk contact. We determined the variation of the state matrix to improve the load/unload performance through comparison of each factor of state matrix.

• 대한전기학회논문지:전력기술부문A
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• 제55권12호
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• pp.514-521
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• 2006

The existing ULTC operation control strategy based on the measured data deteriorates the voltage compensation capability making the efficient corresponding to the load variation difficult by following the fixed load center point voltage. Accordingly, this paper proposes a new on-line fuzzy ULTC controller based on the designed multiple load center points which can improve the voltage compensation capability of ULTC and minimize voltage deviation by moving in real-time the load center point according to the load variation to an adequate position among the multiple load center points designed using the clustering technique. The Max-Min distance technique is adopted as the clustering technique for the decision of multiple load points from measured MTr load current and PTr voltage, and the minimum distance classifier is adopted for the decision of fuzzy output membership function. To verify the effectiveness of the proposed strategy, Visual C++ MFC-based simulation environments is developed. Finally, the superiority the proposed strategy is proved by comparing the fuzzy ULTC operation control results based on multiple load center points with the existing ULTC operation control results based on fixed load center point using the data for three day.

• 전기학회논문지
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• 제58권7호
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• pp.1263-1269
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• 2009

Stable and sustainable power supply means maintaining a certain level of power quality and service while securing energy resource and resolving environmental issues. Distributed generation (DG) has become an essential and indispensable element from environmental and energy security perspectives. It is known that voltage violation is the most important constraint for load variation and the maximum allowable DG. In distribution system, sending voltage from distribution substation is regulated by ULTC (Under Load Tap Changer) designed to maintain a predetermined voltage level. ULTC is controlled by LDC (Line Drop Compensation) method compensating line voltage drop for a varying load, and the sending voltage of ULTC calls for LDC parameters. The consequence is that the feasible LDC parameters considering variation of load and DG output are necessary. In this paper, we design each LDC parameters determining the sending voltage that can satisfy voltage level, decrease ULTC tap movement numbers, or increase DG introduction. Moreover, the maximum installable DG capacity based on each LDC parameters is estimated.

• 한국정밀공학회지
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• 제9권1호
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• pp.126-136
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• 1992

In this paper, a simple structured feedback compensation scheme for a electro-hydraulic servo system to keep the response characteristics unchanged regardless of the load variation is proposed. In electro-hydraulic servo system, servovalve is most important control element. But the relation between input corrent and output flowrate of the servovalve has properties as follows; firstly, in spite of constant input current, output flowrate decreases as load pressure increases, secondly, according to frequency response of typical servovalve, the characteristics of gain and phase shift is something like 2'nd order system. Load pressure feedback compensation method has been applied to eliminate the first influence, the second influence has been improved by phase lead compensation method. As a result of above compensation methods, regardless of variation load condition, spring and inertia load, the compensation scheme has been verified to be effective within the range of frequency less than 25Hz by static response and dynamic response in time domain and frequency domain through experiments.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 학술대회 논문집 정보 및 제어부문
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• pp.303-305
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• 2005

In MMORPG, gamers can engage in a variety of activities with other players from all over the world. So, this kind of games has unprecedented heavy load. There are so many kind of method to balance the load of MMORPG. But. many of them are not adaptable to dynamic load variation. In this paper, we propose a dynamic map-partition method based on VML. By use of dynamic map-partition based on VML, we can easily adapt to dynamic load variation. And by changing VML. we can manage field servers within game system.